1. Field of the Invention
The present invention relates to short-circuit protection circuits and, more specifically, to a circuit for protecting high efficiency IGBTs in a motor controller circuit.
2. Description of the Related Art
A common requirement of IGBT inverters for motor control is that the IGBTs must be able to withstand short-circuits for periods that are in the range of 5 to 10 .mu.s.
The capability of an IGBT to withstand short-circuit for a given period of time is essentially determined by the gain under short-circuit.
At present, two basic types of IGBTs are generally available, namely "short-circuit" types which are designed primarily for motor control applications, and "high-efficiency" types, which are designed for applications where short-circuit capability is not needed, such as switching power supplies. An inherent trade-off exists between these two types of devices. Short-circuit IGBTs (typically designed to withstand short-circuits for up to 10 .mu.s) are inherently less efficient than high-efficiency IGBTs, but the latter have more limited short-circuit capability.
As illustrated by the plots shown in FIG. 1, Gen 4 high-efficiency IGBTs manufactured by the assignee of the present application, International Rectifier Corporation, have about twice the short-circuit current of short-circuit rated types. The greater short-circuit current of the high-efficiency type restricts its short-circuit withstand time to less than a half of that of the short-circuit rated type.
It would be desirable for semiconductor manufacturers such as the present assignee to eliminate the manufacture of short-circuit rated components, in favor of high efficiency types only.
The potential advantages would be:
1. Simplified manufacturing logistics, inventory control, etc., through the manufacture of one basic high-efficiency type of IGBT, instead of two different types; and PA1 2. Better system solutions for applications that require short-circuit capability, with greater design flexibility and improved system performance.